Noooo don't put it In your tank!
I use a garden sprayer from b&q, mix 1 part virosol with 5 parts water. Spray only the frame and plastics on the roof, leave for a couple of minutes then scrub and watch the dirt melt away.
You don't need to spray on the glass of the roof, once on the frames and in your brush head there's more then enough spread around to clean the glass. If the panels are plastic you can spray them though.
If.you do spray directly onto the glass then don't let it dry. In the summer months it's better to wet the roof first.